Like today's trekkers, Leahy noted the unusual nature of the volcanic plateau at the top of Mt Giluwe.

"The space between the two topmost peaks or crags suggested an old crater area," he wrote.

"It must have been a tremendous mountain in its active days."

Leahy and his party descended back down the north side of the mountain, to continue their search for gold in the mountains further north-west.

The local people who live around the mountain can't recall anyone crossing the forbidding massif and descending the other side.

"Previously our forefathers, they have never, ever been that way," local guide Brook Etena said.

"That's our first time."

The purpose of the expedition was not to just to break new ground — it was also to potentially create a new trekking destination in PNG.

"Possibly it's opened up a new area for tourism," Mr Miller said.

"Not just trekking, but these mountains are very rocky so there's a possibility we could set up some cables or steps and stuff and do some via ferrata (climbing routes), which don't exist in Papua New Guinea."